Keyword: Canis lupus, Oncorhynchus spp., Individual specialization, Stable isotope analysis, Predator-prey interactions, Gray wolf https://mc06.manuscriptcentral.com/cjz-pubs Canadian Journal of Zoology Seasonal foraging strategies of Alaskan gray wolves (Canis lupus) in a salmon subsidized ecosystem A.E. Stanek (aestanek@alaska.edu) 1* , N. Wolf (nwolf@uaa.alaska.edu) 1 † , G.V. Hilderbrand (grant_hilderbrand@nps.gov) 2 ‡ , B. Mangipane (buck_mangipane@nps.gov) 3 , D. Abstract Despite frequent observations of wolves (Canis lupus L., 1758) using non-ungulate prey, the seasonal and inter-annual variation in the use and relative importance of alternative prey sources to gray wolf diets have not been studied at the individual scale. We used stable isotope analysis (δ 13 C and δ 15 N) of guard hair and blood components (clot and serum) collected over four years to examine the occurrence, extent, and temporal variation of salmon as a food resource by both individual wolves and social groups in Lake Clark National Park and Preserve in southwestern Alaska. Our results demonstrate substantial variability in the use of salmon over time. During summer, diets of five wolves consisted of at least 50% salmon while the diets of 17wolves consisted of primarily terrestrial prey. Over three years, one group of wolves consistently consumed salmon in summer and switched to terrestrial prey in winter. Prey choices were generally similar within social groups; however, the degree to which individuals consumed salmon was highly variable. The use of salmon as exhibited by wolves in Lake Clark is likely widespread where salmon are abundant and this finding should be taken into consideration in the conservation and management of wolves and their prey.

Borealization is a type of community reorganization where Arctic specialists are replaced by species with more boreal distributions in response to climatic warming. The process of borealization is often exemplified by the northward range expansions and subsequent proliferation of boreal species on the Pacific and Atlantic inflow Arctic shelves (i.e., Bering/Chukchi and Barents seas, respectively). But the circumpolar nearshore distribution of Arctic-boreal fishes that predates recent warming suggests borealization is possible beyond inflow shelves. To examine this question, we revisited two nearshore lagoons in the eastern Alaska Beaufort Sea (Kaktovik and Jago lagoons, Arctic National Wildlife Refuge, Alaska, USA), a High Arctic interior shelf. We compared summer fish species assemblage, catch rate, and size distribution among three periods that spanned a 30-year record (baseline conditions, 1988-1991; moderate sea ice decline, 2003-2005; rapid sea ice decline, 2017-2019). Fish assemblages differed among periods in both lagoons, consistent with borealization.Among Arctic specialists, a clear decline in fourhorn sculpin (Myoxocephalus quadricornis, Kanayuq in Iñupiaq) occurred in both lagoons with 86%-90% lower catch rates compared with the baseline period. Among the Arctic-boreal species, a dramatic 18to 19-fold increase in saffron cod (Eleginus gracilis, Uugaq) occurred in both lagoons.Fish size (length) distributions demonstrated increases in the proportion of larger fish for most species examined, consistent with increasing survival and addition of ageclasses. These field data illustrate borealization of an Arctic nearshore fish community during a period of rapid warming. Our results agree with predictions that Arctic-boreal fishes (e.g., saffron cod) are well positioned to exploit the changing Arctic ecosystem.Another Arctic-boreal species, Dolly Varden (Salvelinus malma, Iqalukpik), appear to have already responded to warming by shifting from Arctic nearshore to shelf waters. More broadly, our findings suggest that areas of borealization could be widespread in the circumpolar nearshore.

Recent studies have noted the differential effects of marine versus terrestrial diets on the carbon and nitrogen stable isotope (13C and 15N, respectively) diet-to-tissue discrimination values and incorporation rates for omnivorous and carnivorous mammals. Inaccurate estimates of these parameters may result in misrepresentation of diet composition or in the timing of diet shifts. Here, we present the results of a diet-switch experiment designed to estimate diet-to-tissue discrimination values and incorporation rates for tissues of gray wolves (Canis lupus Linnaeus, 1758) fed a diet of Pacific salmon (genus Oncorhynchus Suckley, 1861). Our results demonstrate substantial differences in both parameters between wolves maintained on a marine (salmon) diet and wolves maintained on terrestrially sourced prey (beef, Bos taurus Linnaeus, 1758). Increased awareness of the significance of marine resources to omnivorous and carnivorous consumers, like wolves, highlights the importance of phenomenological and mechanistic understandings of the effects of fish and other marine prey on dietary investigations based on stable isotopes.